Almost all women in the western world will some time during their life be investigated morphologically for breast cancer. There are today two main methods for morphological diagnosis of breast lesions, histopathological examination of surgical or core biopsies and cytopathological examination of fine needle aspirates (FNA).
With cytological diagnosis, single cells and small cell complexes are aspirated from the lesion with the aid of a fine needle in which a lowered air pressure is created during the sampling process. Due to the lower adhesion between tumour cells than between healthy cells, the tumour cell concentration in the sample might be enriched. Subsequent to taking the cell sample, the cell material is examined by e.g. ejecting them onto a glass slide, where they are smeared, fixed, stained and examined cytomorphologically. A final diagnosis can be assessed within 10 min reducing the waiting time and the anxiety for the patient. Ongoing advances in genetics and functional genomics suggest that a completely objective molecular diagnostic procedure in single cells from fine needle aspirates will be available in a near future. Today almost all of the operators are using standard hypodermic needles. The most commonly used needle types have an outer diameter between 0.4 mm and 0.8 mm and a length between 25 mm and 50 mm. Ultrasonic guided FNA needles might be even longer, 80 mm or even more.
The diameter of the core biopsy instruments is several times greater than for the FNA needles, with diameters of up to 3.2 mm. Regarding FNA and core biopsy sampling it is of utmost importance to be aware that increasing diameter of the sampling needle is correlated to increasing risk for complications, especially needle tract seeding, local bleeding and infection. In order to minimise the frequency and extension of complications there is a need to establish routines to achieve final diagnosis with needles of minimal diameters. FNA can be performed with virtually no or minimal side effects. Furthermore, the time consumption for the histopathological procedures is considerably longer compared to cytopathological examination making it hard or impossible to incorporate it in “a one-day diagnostic procedure”, which naturally is both economically beneficial and highly demanded from the patients.
However, histopathological examination is able to determine the grade or invasiveness of the tumour, which is not possible using the FNA method. Still the sensitivity and specificity varies greatly with the skill of the aspiration operator and the judging cytologist. If increased sensitivity is reported it is mainly due to a higher degree of sufficient aspirates. In the literature the main reason for choosing core biopsy over FNA is because the frequency of inadequate specimens is lower.
With this in mind it is quite peculiar that standard needles are used for FNA, which are designed for blood sampling or infusion therapy i.e. for quantities of gram when the aspirated sample averages only a few milligrams. Thus, standard needles have large amounts of residual spaces between the Luer coupling and the cannula stainless steel tube, where the sample can stick to the surface and coagulate. The air flow-profile during sample ejection is not well defined and portions of the sample might be sheltered from the air stream during the ejection phase. The needles have residual spaces and registered volumes of more than 70 milligram (of H2O), even when attached to the Record-cone integrated to the syringe. Hence, the compartments are both ill matched in size and configured wrongly to yield optimum amount of sample material. Many experienced FNA-operators are in fact routinely tapping the needle hub against the glass slide to increase the yield. Some even use a small brush to empty the hub from sample. In our studies we have shown that only 25% of the extracted material is obtained on the microscopic glass with a standard 0.6*25 mm needle. The rest is still trapped in the equipment and thrown away after the examination.
If the breast lesions are palpable FNA-sampling is usually performed manually (direct puncture) by the skilled cytological operator, but when lesion size becomes significantly smaller than approx. 10 mm average diameter or are located deeply in the breast, it might be difficult to use the manual puncturing method. Instead ultrasound is nowadays used to guide the needle with high precision. Earlier, stereo-tactic techniques where initially used, but such methods are now used more and more seldom. In the beginning of the ultrasound guided era specially adopted transducers with a guiding needle-channel where often used. However, today a free hand based technique is the most common method. Both the ultrasound transducer and the needle are then held by the operator freely on the non-stabilised breast with the patient lying on her back. This ultrasound guided procedure usually requires a longer needle (up to length 120 mm) and the needle to transducer axis angle becomes quite flat (in the order of 20-30 degrees). The ultrasound frequency commonly used goes from some 3 MHz up to approx. 20 MHz, equivalent to a wavelength-span from 0.5 mm to 0.0745 mm. The λ/4 figure is of course a critical limit for reflection which here becomes approx. 125 μm to 18.6 μm. Due to the flat angle of reflection at the actual wavelength, the reflection intensity can be quite low which means that it can be difficult to accurately follow the needle-tip approaching the tumour structure during the full procedure. Often the motion of the tissue surrounding the needle tip is used to locate the tip. Several methods have been proposed to enhance the ultrasound visibility, as for instance a plastic cover with trapped miniature air bubbles etc. That method however becomes bulky for the thin needle. It is important to optimise the average angle of incidence and reflection plus establish a significant interface difference in acoustic impedance, for the needle material versus the tissues.
Hence, the inventors in the present application have identified the following problems with the FNA technique as it is used today:    1. The obtained sampling yield is too sparse.    2. The ultrasound visibility is too low.    3. The spread of tumour cells in the needle tract (seeding) occurs.
Another issue to attend is the cell sampling of cysts. If a lesion is cystic, generally several millilitres of fluid are obtained. However, the cell material in the fluid will vary significantly. Presently, the sample may for instance undergo centrifugation subsequent to the sampling procedure in order to retrieve the cells to be examined cytomorphologically. This is a rather labour intensive and time consuming procedure and often the retrieved cell concentration is low. Another method is to put a few droplets of the cystic fluid on the microscopic glass and smear it in the same way as solid cell samples. However, the big drawback with this method is that the number of cells examined is usually too few for a conclusive diagnosis.
Still another issue to attend to is the method used to smear the sample on the microscopic glass. Today the sample is smeared using a second microscopic glass, which generally results in considerable loss of sample material due to wetting of the second glass, which is subsequently dismissed.
Some prior art documents are cited in the following.
WO-96/32146 relates to an aspiration needle and method for use in collecting large cell samples with a source of vacuum for fine needle aspiration cytology without increasing the size of the needle having a rigid elongate tubular member having a distal and proximal extremities. A chamber is formed within the tubular member by a sloping uninterrupted wall leading distally to the opening of the member.
U.S. Pat. No. 5,330,443 relates to an aspiration needle for use with a syringe for fine needle aspiration cytology.
WO-2006/036108 relates to an arrangement for cell sampling using fine needle aspiration technique. A longitudinal movement is applied to the needle when the needle is position inside the tumour, and in addition the arrangement is provided with heat generating means in order to apply a short pulse of heat to the needle in order to lower the risk for the tumour to spread.
WO-2006/036112 relates to an arrangement for therapy of tumours where a needle is intended to be inserted into a tumour and radio frequency energy is intended to be applied between the needle and a ground electrode such that heat is generated in tissue surrounding the needle.
Thus, the object of the present invention is to provide an improved needle arrangement for taking a sample of cells from a lesion with the cytological aspiration technique, which provides increased amount of cells in the sample given a certain needle diameter and increased ultrasound visibility in comparison with prior art arrangements.
Another object of the inventive arrangement is to lower the risk of cancer spread when taking the sample.